Because COF packaging enables a semiconductor die to be bonded directly to a multilayer laminate, it has become a key downsizing technology for semiconductor devices. Attaching the die to such a laminate facilitates short lead lengths and a flexible interconnect. Because COF technology requires less space for the I/O interconnects, it minimizes the resulting device's footprint. Driven by the need for miniaturization and flexibility, COF packaging techniques have been adopted for components used in electronic devices such as cameras, pagers, disk drives, LCDs, printers, smart cards, hearing aids and other devices where form factor constraints may be severe.
Although COF packaging technology is currently used for relatively small die with low power requirements, it is not particularly suitable for large, high power die--e.g., a microprocessor die. The large mismatch between the coefficients of thermal expansion ("CTE") of such a die and the molding compound that encapsulates it can create significant stress and warpage, which can cause reliability failures and processing difficulties. In addition, a highly powered die generates significant heat that must be dissipated to maintain an acceptable servicing temperature. Because COF packaging encloses the back side of the die with the molding compound, such packaging does not efficiently conduct heat.
Accordingly, there is a need for an improved COF packaged device that does not sustain severe stress or warpage caused by large CTE mismatch between the die and the molding compound. In addition, there is a need for such a device that may effectively transfer heat from the die.